PvP Moveset Explanation
Psycho Cut or Confusion + Moonblast and Future Sight or Grass Knot*
Psycho Cut (1.5 DPT/4.5 EPT) gives Cress the ability to fire off charged moves far faster, at the cost of making her much less effective when your opponent still has shields available...
PVE Overview
Cresselia is a sitting lunar duck for punishment, which is fine in the main series Pokemon games, where it can stall opponents to death. For now, the only targets that it can stall to death in GO are players battling it in a raid.
PVE Offensive Moves Explanation
•Pick Confusion over Psycho Cut, especially for the bulky Cresselia.
•Only lunatics would use Cresselia, but go with Future Sight if you do.